Organic polymeric films such as polyimides are commonly employed in the semiconductor and packaging industry. Typical flexible circuit fabrication requires the use of metallized organic polymer films. Under normal process conditions, a seed or catalyst layer is sputtered or evaporated onto the polymer film. In current metallization processes, continuous treatment is required to develop uniform and reproducible film characteristics. A general process requires the preparation of the polymeric film by a series of thermal and vacuum treatments, followed by surface modification in plasmas or glow discharges, and sequential deposition of an adhesion-promoting layer chromium and copper seed layer.
The direct metallization of polymides such as Kapton.RTM.-H with copper had resulted in less than satisfactory adhesion at the copper-polyimide interface. In particular, problems have occurred at the copper-polyimide interface resulting in lifting up of the copper line from the underlying polyimide substrate rendering the carrier unsuitable for its intended purpose.
Accordingly, in order that the configurations which involve a copper-polyimide interface be competitive in a commercial environment, it is necessary to improve the adhesion at the copper-polyimide interface. The importance of improving the adhesion between such substrates and the metallic layers cannot be overemphasized.